Sporotrichosis Causes and Risk Factors

The disease, sporotrichosis, is caused by the fungus Sporothrix schenckii, although recent research has shown that several other distinct Sporothrix species also cause the disease. However, the disease progresses similarly for these closely related fungal species:

Sporotrichosis usually begins when fungal spores are forced under the skin by a rose thorn or sharp stick.

The infection may also begin in apparently unbroken skin after contact with hay or moss carrying the fungus.

Farmers, nursery workers, landscapers, and gardeners are at higher risk for the disease because of their chance of cuts or puncture wounds while working with soil. People who are immunosuppressed (HIV patients, cancer patients, for example) are also at higher risk to get the disease.

Rarely, cats or armadillos can transmit the disease to humans with scratches from the animal's claws.

In very rare cases, the organism can be inhaled or ingested, leading to infection of parts of the body other than the skin; this type of infection may also occur from advanced skin infections in people who are immunosuppressed.

The disease does not appear to be transmitted from person to person; some investigators consider sporotrichosis to be a self-limited mycosis (fungal infection not transmitted to other people).

The fungus is dimorphic (can exist as a yeast-like or hyphae-producing form). The figure below shows the hyphae (the long, filamentous parts) and conidia (spores) of Sporothrix schenckii.